1. Field of the Invention
The invention relates to content protection technologies, and in particular, to content control technologies for storage systems.
2. Description of the Prior Art
Content protection and control has become an important issue for both content providers and individual users. Content typically takes the form of digitally formatted data structures, such as simple data files, music files, video files, e-mails, word processing files, and photos, as well as other types of content. Content providers, such as multi-media companies, are often times concerned with content piracy issues and desire to limit the illicit copying and distribution of content. Individual users are often times concerned with privacy issues and desire to protect against personal harms, such as identify theft.
Most devices, such as mobile phones, personal computers, personal digital assistants, music devices, and video devices, as well as other devices, include a host system and a storage system. The storage system typically includes a storage medium and a control system. The control system is sometimes located on the host system. The control system interfaces with the host system to store and retrieve content to and from the storage medium. In addition to the host system, storage system, and control system, most devices have software that operates in accordance with a well known software model that includes an application layer, the operating system layer, and the hardware layer. The application layer is the uppermost layer in the hierarchy. The operating system typically functions to interface between the application layer and the hardware layer.
One problem with many devices is that storage systems can be easily removed from their associated host systems and ported to new host systems. This reduces the effectiveness of many prior art content protection schemes that seek to prevent unauthorized access to the host system. For example, mobile phones often times include the option of a user password to protect against the unauthorized use of the phone. In another example, network operators can remotely disable media devices, thereby preventing unauthorized access to the host system. Unfortunately, even when a user cannot gain access to a host system due to a secure login mechanism, the entire storage system can be removed from the device and ported to a new, unprotected host system.
Most software based protection schemes are also notoriously unreliable and suffer from systemic vulnerabilities. For example, software protection schemes typically utilize open memory space that can be easily hacked. In addition, most software protection schemes operate in the application layer above the operating system layer. As a result, most software protection is vulnerable due to the inherent liabilities of the operating system upon which it relies.
One prior art example of a purely software oriented approach to security involves encrypting content, such as a word processing document, with a user defined password. The content is encrypted in the application layer while resident on a host system and subsequently transferred in its encrypted form to a storage system. One problem with this method is that the content is still accessible on the storage medium, although in an encrypted form. In addition, while the user retains control over the content via the user defined password, the encrypted content can still be copied and ported to other host systems. For example, a music file stored on flash memory could be ported from a first device to another device. In the case of high value content, such as a music or movie file, the original content provider may desire to limit such capabilities.
In response to the deficiencies of software protection schemes, many hybrid hardware and software based protection schemes have been implemented in the prior art. In one example, a hardware serial number is used to identify a host system to a remote content system, such as a web server, when the host system attempts to access the remote content system. In yet another example, a private and public key pair is generated using a hardware serial number. A host system encrypts and decrypts content using the private key before sending and receiving the content to and from a remote content system. The remote content system decrypts and encrypts the content using the public key. However, neither protecting access to a remote content system from unauthorized host systems, nor encrypting content using a key derived from a hardware serial number, limits access to content once it has been legitimately downloaded to a storage system.
Another example of hybrid prior art content protection involves a specialized microcontroller designed to provide basic security-related functions to the software utilizing the microcontroller. In this prior art design, the microcontroller contains a hardwired code, such as a private key, that is used to decrypt content that has been previously encrypted with a public key. One disadvantage of this design is that the microcontroller outputs data regardless of the destination for the data. While the data may remain in an encrypted form, it becomes vulnerable to various attacks once it has left the microcontroller. In addition, such encryption and decryption processes are often times overly resource intensive and time consuming.
In yet another example of the prior art, access to a storage system is protected by a basic input output system (BIOS) enforced password. The correct password must be provided to the BIOS before the storage system can be accessed in the course of a normal boot up process. Any content that is stored on the storage system is inherently protected by a BIOS password protection scheme. A drawback is that once the BIOS receives the correct password, unfettered access is granted to the storage system and the content stored on the storage system is left unprotected.